Single step process for the preparation of lower alpha-alkene polymerization heterogeneous solid catalyst

ABSTRACT

Single step process for the preparation of lower α-alkene polymerisation heterogeneous solid catalyst, wherein the procatalyst is obtained by reacting organomagnesium precursor and titanium tetrahalide or titanium haloalkoxo species of the formula Ti(OR)m Xn, with a hydrocarbon or halohydrocarbon solvent and internal electron donor and optionally an acid halide under microwave irradiation of 300 to 1200 W. The mole ratio of the organomagnesium precursor to the titanium tetrachloride or titanium haloalko species is 1:6 to 1:20 and the mole ratios of the electron donor and acid halide to titanium is 0.3 to 1.5 and 0.02 to 0.2, respectively.

This invention also relates to lower α-alkene polymerisationheterogeneous solid catalyst obtained by the single step process andprocess for the polymerization of lower α-alkene using the heterogeneoussolid catalyst.

BACKGROUND ART

Polymers of lower α-alkene or olefins such as ethylene, propylene or1-butene find applications in the manufacture of a variety of articlesincluding plastic bags or sheets or automobile parts. Of particularinterest in polymer production are polyethylene and polypropylene with ahigh degree of isotacticity i.e. the extent of orientation of thebranched groups in the polymer in the same direction, which shows highcrystallinity. The polymerisation involves reacting the lower α-alkenesuch as ethylene or propylene with catalyst under polymerisationconditions. The early polymerisation on catalysts were of relatively lowactivity and the polymers formed contained significant amounts of thecatalyst residues, which had to be removed by deashing. The more recentalkene polymerisation catalysts are of two types viz. single sitecatalysts and heterogeneous solid catalysts. The single site catalystscomprise metallocene and non-metallocene complexes of transition metalsand a cocatalyst such as methyl aluminoxane and produces polymer of lowpolydispersity.

Heterogeneous solid catalysts are the most commonly used catalysts,especially in the bulk production of polyethylene or polypropylene dueto their high activity and ease of operation. These catalysts aresometimes referred to as heterogeneous Ziegler-Natta catalysts. Aheterogeneous solid catalyst comprises a procatalyst and a cocatalystand for polypropylene with high isotacticity an external selectivitycontrol agent or external electron donor also. The cocatalyst may be anorganoaluminium compound such as alkyl aluminium. The physicochemicalproperties of the procatalyst play a pivotal role in the overallperformance of the catalysts. The procatalysts comprise organomagnesiumor magnesium chloride derived precursor comprising magnesium chloridesupported titanium chloride and an internal electron donor. Theprocatalysts are synthesised by halogenation of an organomagnesiumcompound such as magnesium ethoxide with a halogenating agent such astitanium tetrahalide in a hydrocarbon or halohydrocarbon solvent such astoluene or chlorobenzene optionally with an acid halide to formmagnesium chloride. The magnesium chloride so obtained is reacted withtitanium haloalkoxide or excess titanium tetrahalide, usually titaniumtetrachloride in the presence of a hydrocarbon or a halohydrocarbonsolvent. To this an internal electron donor is added simultaneously orsequentially to result in a procatalyst (U.S. Pat. Nos. 4,400,302,4,414,132, 4,497,905, 4,535,068, 4,657,995, 4,710,482, 4,728,705,4,771,024, 4,804,648, 4,870,039, 4,914,069, 4,870,040, 5,066,737,5,077,357, 5,106,806, 5,082,907, 5,122,494, 5,124,298, 5,141,910,5,151,399 and 5,229,342). In most of the above processes employingorganomagnesium compounds or silica coated with organomagnesiumcompounds, the procatalyst preparation involves treatment of themagnesium precursor with titanium tetrahalide more than once, so thatcatalysts of optimum titanium loading and activity are obtained. U.S.Pat. Nos. 4,400,302 and 4,414,132 teach that at least two treatmentswith titanium tetrahalide are required for catalysts with high activity.In U.S. Pat. Nos. 4,497,905, 4,535,068 and 4,657,995, where ahalogenating agent is used to enhance activity, several treatments withtitanium tetrachloride are described. The total amount of titaniumtetrahalide required for multiple treatments are also considerable.

Procatalyst also may be prepared by milling together anhydrous magnesiumchloride, a titanium tetrahalide such as titanium tetrachloride and forpolypropylene catalyst an internal electron donor (U.S. Pat. Nos.4,329,253, 4,393,182 and 4,419,501). Preparation of procatalysts by thisphysical method requires very long milling time. Furthermore when usedin polymerisation reactions, procatalysts obtained by milling in generalshow activities and selectivities inferior to those obtained by chemicalmethod.

Several processes and products employing microwave energy are reportedin patent literatures. PCT Publication No WO2001028771 describesmicrowave curable compositions comprising at least one heat curableresin component, microwave absorbable particles in an amount of about10% of the composition, and at least one curing agent for the heatcurable resin component. European Patent no 992480 describes thepreparation of methacrylate and polyester methacrylates in the presenceof a catalyst and inhibitor under microwave heating. U.S. Pat. Nos.6,017,845 and 6,171,479 describe a process that involves a catalystcomprising a support, a microwave absorption material and catalyticallyactive phase. On heating the catalyst with a source of microwave energy,the microwave absorption material absorbs the energy and increases thetemperature of the catalyst to the desired level. The heated catalyst iscontacted with a hydrocarbon feedstock for upgrading. PCT Publication NoWO 9743230 describes a method for palladium catalyzed organic reactionsheated with microwave energy in solution. U.S. Pat. No. 5,194,514describes the use of microwave in the presence of paramagnetic catalyststo increase molecular weight of the polymer. U.S. Pat. No. 5,719,095describes supported catalyst system comprising support, at least onemetallocene catalyst fixed to the support, and at least one cocatalyst,wherein the catalyst is fixed to the support by bringing the catalystinto contact with a supported cocatalyst in a suspension and irradiatingwith microwaves.

OBJECTS OF INVENTION

An object of the invention is to provide single step process for thepreparation of lower α-alkene polymerisation heterogeneous solidcatalyst which simplifies the preparation procedure and shortens thepreparation time.

Another object of the invention is to provide single step process forthe preparation of lower α-alkene polymerisation heterogeneous solidcatalyst which reduces the amount of titanium tetrahalide required andis economical.

Another object of the invention is to provide single step process forthe preparation of lower α-alkene polymerisation heterogeneous solidcatalyst, which when used in polymerisation of ethylene and propyleneshows high activity and selectivity and for propylene results inpolymers with high isotacticity index.

DETAILED DESCRIPTION OF INVENTION

According to the invention there is provided a single step process forthe preparation of lower α-alkene polymerisation heterogeneous solidcatalyst comprising an organomagnesium precursor derived procatalystcomprising magnesium chloride supported titanium chloride and aninternal electron donor and an organoaluminium compound basedcocatalyst, wherein the mole ratio of aluminium the cocatalyst totitanium in the procatalyst is 10-3000:1 and the procatalyst is obtainedby single step reaction of organomagnesium precursor and titaniumtetrahalide or titanium haloalkoxo species of the formula Ti(OR)m Xn,wherein R is methyl, ethyl, normal or isopropyl, normal or isobutyl,preferably n-butyl, X is chlorine or bromine, preferably chlorine andm+n=4 with the condition that when m=1-4, n=3-0 respectively with ahydrocarbon or halohydrocarbon solvent and internal electron donor andoptionally an acid halide under microwave irradiation of 300 to 1200 Wfollowed by isolating the procatalyst, the mole ratio of theorganomagnesium precursor to the titanium tetrachloride or titaniumhaloalko species being 1:6 to 1:20 and the mole ratios of the electrondonor and acid halide to titanium being 0.3 to 1.5 and 0.02 to 0.2,respectively.

According to the invention there is also provided a single step processfor the preparation of polypropylene polymerisation heterogeneous solidcatalyst comprising an organomagnesium precursor derived procatalystcomprising magnesium chloride supported titanium chloride and aninternal electron donor and an organoaluminium compound based cocatalystand a selectivity control agent, wherein the mole ratio of aluminium inthe cocatalyst to titanium in the procatalyst is 10-3000:1 and the moleratio of selectivity control agent to titanium is 10-100:1 and theprocatalyst is obtained by single step reaction of organomagnesiumprecursor and titanium tetrahalide or titanium haloalkoxo species of theformula Ti(OR)m Xn, wherein R is methyl, ethyl, normal or isopropyl,normal or isobutyl, preferably n-butyl, X is chlorine or bromine,preferably chlorine, m=0 and n=4 with a hydrocarbon or halohydrocarbonsolvent and an internal electron donor and optionally an acid halideunder microwave irradiation of 300 to 1200 W followed by isolating theprocatalyst, the mole ratio of the organomagnesium precursor to thetitanium tetrachloride or titanium haloalko species being 1:6 to 1:20and the mole ratios of the electron donor and acid halide to titaniumbeing 0.3 to 1.5 and 0.02 to 0.2 respectively.

Preferably the mole ratio of the aluminium in the cocatalyst to thetitanium the procatalyst of the catalyst is 200:1.

The heterogeneous solid procatalyst may have a surface acrea of 40-300m²/g, preferably 50-200 m²/g.

The titanium tetra halide may be titanium tetra chloride or bromide,preferably titanium tetra chloride.

The organomagnesium precursor such as magnesium ethoxide and anhydrousmagnesium chloride used for preparation of the procatalyst arecommercially available or prepared in known manner. Other magnesiumalkoxides such as methoxide, normal and isopropoxide, normal andisobutoxide and 2-ethyl butoxide may also be used but the preferredorganomagnesium precursor is magnesium ethoxide.

The hydrocarbon or halohydrocarbon solvent used in the reaction must becapable of absorbing microwave energy and may be hexane, methylcyclohexane, toluene, xylene, chlorobenzene, dichlorobenzene oro-chlorotoluene, the preferred solvent being chlorobenzene.

Preferably, a microwave energy of 300 W is applied.

The isolation of the procatalyst involves filtration, washing with ahydrocarbon solvent such as toluene and drying of the solid.

The organoaluminium cocatalyst may be trialkyl or mixed halo alkyl oralkoxo aluminium compounds usually employed with titanium procatalysts.These may be commercially available or prepared in known manner.Preferably triethyl aluminium is used.

Preferably, the mole ratio of the organomagnesium precursor to thetitanium tetrachloride or titanium haloalko is 1:13.

The selectivity control agent is an ester such as p-substituted benzoateor phthalate, preferably p-ethoxy ethyl benzoate or an ether such asalkyl alkoxy or aryl alkoxy silane. Preferably dicyclohexyl dimethoxysilane or diphenyl dimethoxy silane usually employed with titaniumprocatalysts are used. The selectivity control agents may becommercially available or prepared in known manner. Preferably the moleratio of the selectivity control agent to the titanium in theprocatalyst is 10-75:1.

The internal electron donor may be esters of benzoic acid or diesters ofphthalic acid preferably ethyl benzoate, dibutyl or diisobutylphthalate.

The acid halide may be halide of an aliphatic or aromatic acidpreferably benzoyl chloride.

Preferably the molar ratios of the electron donor and acid halide if anyto titanium are 0.7 and 0.07, respectively.

The constituents of the polymerisation catalyst viz. procatalyst andcocatalyst and optionally selectivity control agent may be mixed in avessel outside the polymerisation reactor before being transferred tothe polymerisation reactor. Alternatively, the constituents may beindividually transferred into the polymerisation reactor to generate theactive catalyst in situ.

The lower α-alkenes used for polymerisation may be ethylene, propylene,1-butene or 1-hexene to produce homopolymers or copolymers. Preferablyethylene or propylene is used. The polymerisation may be conducted withone or more lower α-alkene to produce homopolymers or copolymers, in thegas phase employing one or more fluidized beds of catalysts in knownmanner. Alternatively, the polymerisation may be conducted in the slurryphase in the absence or presence of an inert hydrocarbon diluent such ashexane in known manner.

According to the invention the polymerisation catalyst is prepared inone step reaction. This simplifies the procatalyst manufacturingprocedure and reduces the batch time. The amount of titanium tetrahalideused for making the procatalyst is also reduced thereby rendering theprocess economical. The procatalyst prepared by the process of theinvention shows high activity and selectivity, particularly in producingpolymers with high isotacticity index.

The following experimental examples are illustrative of the inventionbut not limitative of the scope thereof.

EXAMPLE 1

Magnesium ethoxide (10 gm) and TiCl₄ (131 ml) diluted with chlorobenzene(131 ml) were placed inside a multi necked quartz flask equipped withnitrogen inlet, electronic temperature sensor probe and refluxcondenser. The mixture was magnetically stirred and the temperature ofthe mixture was maintained at 110° C. for one hour under microwaveradiation 300W. The yellowish solid formed was filtered, washed twicewith hexane and dried under a stream of nitrogen.

EXAMPLE 2

Magnesium ethoxide (10 gm) and TiCl₄ (90 ml) and Ti(OBu^(n))₄ (40 ml)diluted with chlorobenzene (131 ml) were placed inside a multi neckedquartz flask equipped with nitrogen inlet, electronic temperature sensorprobe and reflux condenser. The mixture was magnetically stirred and thetemperature of the mixture was maintained at 110° C. for one hour undermicrowave radiation 300W. The yellowish solid formed was filtered,washed twice with hexane and dried under a stream of nitrogen.

EXAMPLE 3

Magnesium ethoxide (10 gm) and TiCl₄ (131 ml) diluted with chlorobenzene(131 ml) in the presence of ethyl benzoate (8.4 ml) and benzoyl chloride(0.7 ml) were placed inside a multi necked quartz flask equipped withnitrogen inlet, electronic temperature sensor probe and refluxcondenser. The mixture was magnetically stirred and the temperature ofthe mixture was maintained at 110° C. for one hour under microwaveradiation 300W. The yellowish solid formed was filtered, washed twicewith hexane and dried under a stream of nitrogen.

EXAMPLE 4

Magnesium ethoxide (10 gm) and TiCl₄ (131 ml) diluted with chlorobenzene(131 ml) in the presence of diisobutyl phthalate (3.9 ml) and benzoylchloride (0.7 ml) were placed inside a multi necked quartz flaskequipped with nitrogen inlet, electronic temperature sensor probe andreflux condenser. The mixture was magnetically stirred and thetemperature of the mixture was maintained at 110° C. for one hour undermicrowave radiation (300W). The yellowish solid formed was filtered,washed twice with hexane and dried under a stream of nitrogen.

EXAMPLE 5

Anhydrous magnesium chloride (10 gm) and TiCl₄ (131 ml) diluted withchlorobenzene (131 ml) in the presence of ethyl benzoate (8.4 ml) wereplaced inside a multi necked quartz flask equipped with nitrogen inlet,electronic temperature sensor probe and reflux condenser. The mixturewas magnetically stirred and the temperature of the mixture wasmaintained at 110° C. for one and a half hour under microwave radiation300W. The yellowish solid formed was filtered, washed twice with hexaneand dried under a stream of nitrogen.

EXAMPLE 6

Anhydrous magnesium chloride (10 gm) and Ti(OBu^(n))₄ (170 ml) dilutedwith chlorobenzene (170 ml) were placed inside a multi necked quartzflask equipped with nitrogen inlet, electronic temperature sensor probeand reflux condenser. The mixture was magnetically stirred and thetemperature of the mixture was maintained a 110° C. for one and a halfhour under microwave radiation 600W. The pale yellow solid formed wasfiltered, washed twice with hexane and dried under a stream of nitrogen.

EXAMPLE 7

In the presence of cocatalysts and for propylene in the presence ofexternal electron donors, the procatalysts obtained in Example 1 to 6were used for polymerization reactions of lower α-alkenes. Thepolymerization data are given in the following Table. The polymerizationreactions were carried out under two sets of conditions: A and B.Polymerizations under conditions A were carried out in the slurry phasewith hexane as the diluent under a constant pressure of 5 Kg for 1 hr at70° C. The procatalyst (0.1 gm) was mixed with triethyl aluminiumcocatalyst (1.425 gm) and for propylene either p-ethoxy ethyl benzoate(0.61 gm) or dicyclohexyl dimethoxy silane (0.15 gm) as the selectivitycontrol agent. Polymerization under conditions B were carried out in theslurry phase with hexane as the diluent under atmospheric pressure at30° C. The procatalyst (0.1 gm) was mixed with triethyl aluminiumcocatalyst (1.425 gm) and for propylene either p-ethoxy ethyl benzoate(0.61 gm) or dicyclohexyl dimethoxy silane (0.15 gm) was used as theselectivity control agent. TABLE Polymer yield (gm per 0.1 gm ofprocatalyst)/ Procatalyst α-Alkene Condition Selectivity Example 1Ethylene A 450 Example 2 Ethylene A 400 Example 3 Propylene B 300/96%Example 4 Propylene B 280/97.5% Example 5 Propylene B 150/96% Example 6Ethylene A 350

The table shows that the catalyst prepared by the single step processhas excellent activity and selectivity for the polymerization ofethylene and propylene.

1. Single step process for the preparation of lower α-alkenepolymerization heterogeneous solid catalyst comprising anorganomagnesium precursor derived procatalyst comprising magnesiumchloride supported titanium chloride and an internal electron donor andan organoaluminum compound based cocatalyst, wherein the mole ratio ofaluminum in the cocatalyst to titanium in the procatalyst is 10-3000:1and the procatalyst is obtained by single step reaction of theorganomagnesium precursor and titanium tetrahalide or titaniumhaloalkoxo species of the formula Ti(OR)m Xn, wherein R is selected fromthe group consisting of methyl, ethyl, normal propyl, isopropyl, normalbutyl, and isobutyl, X is selected from the group consisting of chlorineand bromine, and m+n=4 with the condition that when m=1 to 4, n=3 to 0respectively with a hydrocarbon or halohydrocarbon solvent and internalelectron donor and optionally an acid halide under microwave irradiationof 300 to 1200 W followed by isolating the procatalyst, the mole ratioof the organomagnesium precursor to the titanium tetrachloride ortitanium haloalko species being 1:6 to 1:20 and the mole ratios of theelectron donor and acid halide to titanium being 0.3 to 1.5 and 0.02 to0.2, respectively.
 2. Single step process as claimed in claim 1, whereinthe organomagnesium precursor is magnesium ethoxide.
 3. Single stepprocess as claimed in claim 1, wherein the mole ratio of theorganomagnesium precursor to the titanium tetrachloride or titaniumhaloalkoxo species is 1:13.
 4. Single step process as claimed in claim1, wherein the titanium tetrahalide is titanium tetrachloride.
 5. Singlestep process as claimed in claim 1, wherein the mole ratio of aluminumin the cocatalyst to titanium in the procatalyst is 200:1.
 6. Singlestep process as claimed in claim 1, wherein the solvent ischlorobenzene.
 7. Single step process as claimed in claim 1, wherein themicrowave radiation of 300 W is applied.
 8. Single step process asclaimed in claim 1, wherein the organoaluminum compound is triethylaluminum.
 9. Single step process as claimed in claim 1, wherein themolar ratios of the electron donor and acid halide, if any, to titaniumare 0.7 and 0.07 respectively.
 10. Single step process as claimed inclaim 1, wherein the electron donor is selected from the groupconsisting of ethyl benzoate, dibutyl and diisobutyl phthalate. 11.Single step process as claimed in claim 1, wherein the acid halide isbenzoyl chloride.
 12. Lower α-alkene polymerisation heterogeneous solidcatalyst obtained by the single step process as claimed in claim
 1. 13.Single step process for the preparation of polypropylene polymerizationheterogeneous solid catalyst comprising an organomagnesium precursorderived procatalyst comprising magnesium chloride supported titaniumchloride and an internal electron donor and an organoaluminum compoundbased cocatalyst and a selectivity control agent, wherein the mole ratioof aluminum in the cocatalyst to titanium in the procatalyst is10-3000:1 and the mole ratio of selectivity control agent to titanium is10-100:1 and the procatalyst is obtained by single step reaction oforganomagnesium precursor and titanium tetrahalide or titaniumhaloalkoxo species of the formula Ti(OR)m Xn, wherein R is selected fromthe group consisting of methyl, ethyl, normal propyl, isopropyl, normalbutyl, and isobutyl, X is selected from the group consisting of chlorineand bromine, m=0 and n=4 with a hydrocarbon or halohydrocarbon solventand an internal electron donor and optionally an acid halide undermicrowave irradiation of 300 to 1200 W followed by isolating theprocatalyst, the mole ratio of the organomagnesium precursor to thetitanium tetrachloride or titanium haloalko species being 1:6 to 1:20and the mole ratios of the electron donor and acid halide to titaniumbeing 0.3 to 1.5 and 0.02 to 0.2 respectively.
 14. Single step processas claimed in claim 13, wherein the organomagnesium precursor ismagnesium ethoxide.
 15. Single step process as claimed in claim 13,wherein the mole ratio of the organomagnesium precursor to the titaniumtetrachloride or titanium haloalkoxo species is 1:13.
 16. Single stepprocess as claimed in claim 13, wherein the titanium tetrahalide istitanium tetrachloride.
 17. Single step process as claimed in claim 13,wherein the mole ratio of aluminum in the cocatalyst to titanium in theprocatalyst is 200:1.
 18. Single step process as claimed in claim 13,wherein the solvent is chlorobenzene.
 19. Single step process as claimedin claim 13, wherein the microwave radiation of 300 W is applied. 20.Single step process as claimed in claim 13, wherein the organoaluminumcompound is triethyl aluminum.
 21. Single step process as claimed inclaim 13, wherein the selectivity control agent is selected from thegroup consisting of p-ethoxy ethyl benzoate, dicyclohexyl dimethoxysilane and diphenyl dimethoxy silane.
 22. Single step process as claimedin claim 13, wherein the mole ratio of the selectivity control agent totitanium is 10-75:1.
 23. Single step process as claimed in claim 13,wherein the molar ratios of electron donor and acid halide, if any totitanium are 0.7 and 0.07, respectively.
 24. Single step process asclaimed in claim 13, wherein the electron donor is selected from thegroup consisting of ethyl benzoate, dibutyl phthalate, and diisobutylphthalate.
 25. Single step process as claimed in claim 13, wherein theacid halide is benzoyl chloride.
 26. Polypropylene polymerizationheterogenous solid catalyst obtained by the single step process asclaimed in claim
 13. 27. (canceled)